Coherent states have been introduced in a physical context, first as quasi-classical states in quantum mechanics, then as the backbone of quantum optics and they are described in that spirit in the article Coherent states (see also). However, they have generated a huge variety of generalizations, which have led to a tremendous literature in mathematical physics. In this article, we sketch the main directions of research on this line. For further details, we refer to several existing surveys .
Let be a complex, separable Hilbert space, a locally compact space and a measure on . For each in , denote a vector in . Assume that this set of vectors possesses the following properties: